Automatic telephone system



' Dec. 10, 1929. H. R. PARSHALL 1,739,178

AUTOMATIC TELEPHONE SYSTEM Filed Oct. 25. 1926 QU@ @is a K L lq o to KTv NIN 'Harry E Fal-'shall Patented Dec. 10, 1929 UNITED STATES PATENTOFFICE HARRY R. PARSHALL, F CHICAGO, ILLINOIS, ASSIGNOR TOAUTOMATICiELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF'DELAWAREY AUTOMATIC TELEIHONE SYSTEM Application filed October 23, 1926. SerialNo. 143,558.

This invention relates to telephone systems in general, but moreparticularly to small automatic telephone systems.

In'small systems of this type it is customary that all of the specialservice trunks, for

instance, information, complaint, intercepting, and inspectors trunks,terminate in a single switchboard on account of the fact that there arenot sufcient calls of thisnature to warrant separate positions for eachtype of service. A Single operator or attendant is capable of handlingall the calls coming into such a switchboard. The invention relates toequipment used by the operator for handling calls coming in at theswitchboard and more particularly to an improved single plug ended cordcircuit arranged for extending calls either through the cord circuitfrom a calling to a called subscriber, or direct from the operator to acalled subscriber when the operator is the calling party.v

The various features of the invention will be described in detail in thefollowing specilication in connection with theexplanation of theoperation of t-he various circuits which are described with the aid ofthe accompanying drawings.

Referring now to the drawing, there is shown by means of the usualcircuit diagram a trunk circuit TC, an improved single plug ended cordcircuit CC, an operators headset O, and a rotary lineswitch LS forextending calls.

rEhe trunk circuit TC and similar trunk circuits extend from the banksof automatic Strowger selector switches in thev regular trunkingarrangement and terminate at the switchboard in jacks such as jack J. Atrunk circuit of this type may be used for handling complaint orinformation calls, or may be used as an inspectors trunk.

The cord circuit CC at the operators position terminates in one end inthe plug P and at the other end in the conductors 45 and 46 which extendthrough an intermediate distributing frame to a; rotary lineswitch LS.In the cord circuit CC there is provided a two-way, locking, lever typekey TK and DK used for talking when operated in one direction and fordialing when operated in the opposite direction. The key as shown is innormal or neutral position. A'number of relays are also shown in thiscord circuit, the circuits of which in combination with the talking anddialing keys permit special operating features to be performed.

rIhe operators headset O shown directly above the cord circuit isprovided with a calling device CD and the usual instrumentalities forpermitting her to converse with either the calling or called subscriber.

The lineswitch LS is located in the automatic switchroom and is of thewell known rotary' type, in which the wipers have no normal position andremain in the position last used. The rotary lineswitch LS has access toselector switches in the regular trunking arrangement of the automaticexchange thereby enabling the operator to extend a connection orcomplete a connection to any one of the subscribers in the automaticexchange.

Vith this general description of the drawings in mind, the operation ofthe circuits may now be explained in detail. For this purpose, it willlirst be assumed that an inspector is calling in on the trunk circuitand that it becomes necessary for the operator to extend the callthrough the regular train of switches to a subscribers line. The callingparty dials the proper digits to trunk the call through the automaticswitches to an idle trunk circuit, which we will assume is the trunkcircuit TC. When the selector yseizes the trunk circuit TC, which itdoes over Vconductors 1, 2, and 3, relay 5 energizes over the followingcircuit: from ground through the upper winding of relay 5, armature 13and its resting contact, conductor 1, through the calling partys loop,conductor 3, resting contact of armature 14 and said armature, and lowerwinding of relay 5 to battery. Relay 5, upon energizing, closes atarmature 10 and its working contact a circuit for lighting the call lampL; at armature 11 and its working contact connects the ring back tonemachine RB to the calling line in the well known manner; and at armature12 and its working contact closes a circuit for energizing slow actingrelay 4. Relay 4, upon energizing, prepares a locking circuit for relay7 at armature 9 and its Working Contact; and at armaturel 8 and itsWorking contact connects ground to the release trunk conductor 2,thereby making the trunk circuit TC busy to r other selectors havingaccess thereto and providing a holding circuit for the operatedswitches. Y

The operator at the switchboard perceiving the lighted condition of thelamp Linserts the plug P ofthe cord circuit-'GC into the u jack J of thetrunk circuit TC. Responsive to the insertion of the'plug P into the.

jack J, a. circuit is closed for energizing relays 6 and 7 of the trunkcircuit T] and the u relay 2O ot the cord circuit CC in series, asfollows: from ground by Ways-ot armature and lits resting contact,restingcontact controlled by spring 38 ofthe dial key ,DK- and saidspring, relay 20, sleeve conductor of plug ,A l), sleeve of ack J,spring 19 and-its Working contact, upper winding'of relay 7,- andWinding of relay 6 to battery. Relay 6, upon energizing over the abovetraced circuit, opens at armatures 13 and 14 thecircuit ,for relay 5;and at armature 15 land its Working 'contact maintains the slowacting-relay 4 en-V ergized. Relay 7 upon energizing, at armature 18 andits resting contact disconnects the ring back tone machine RB; atarmature l17 .closes a locking circuit for itself-,and at armature 16extinguishes lamp L andV prepares a circuit for lamp L. Relay 5, upondeenergizing, at armature 12 opens `the origina-l ergizing circuit ofrelay 4, which vhowever is now maintained energized from ground atarmature 15. It may be mentioned here, that the disconnection ot' thering back tone ir.- dicates to the calling party that the operator hasanswered.

In the cord circuit CC relay 20, upon energizing, disconnects resistance85 and battery from armature 36, and at armature opens a point in thecircuit orn relay 21. lt will be noted that the relay 22 is shortcircuited by the dial key DK at springs 33 and its resting contact.Relay `22'is prevented from operating by this shunt circuit so as not-toinitiate the operation of the linesWitCh LS.' With this arrangement thelinesvvitchis prevented from operating and ldoes. not therefore tie up atrunk at this time.

After the insertion of plug P into'the jack J, the operator or attendantatthe switchboard will operate the talk key TK and converse with thecalling party. By the operation ofthe talk key TK, the operators headsetO is connected directly across the .trunln It `Will' be observed lthatthe retardation coil 25 furnishes talkingbatteryfor the calling partythrough i resting vcontacts -on-v armatures 39. and 42.

The operator or attendant, upon ascertaining that it is Ydesirabletoconnect the calling party with an automatic subscriber in theexchange,restores the talk key .TK and operates the dial key DK. Responsive tothe operation of dial key DK, spring 33 and its resting contact areseparated thereby rendering effective a circuit for operating relay 22in series With the sleeve relay 20. At the dial key springs 32 and 34,the cord circuit is divided into two sections and the operators callingdevice CD is bridged across the talking conductorsrof the outgoingsection. Relay-22,jupon energizing, `over the above traced'circuitcloses at armature 40 andv its .Working contacta circuit for theelectropolarized relay 23 (not operated at this time), a-.circuit-orlighting supervisory lamp L2; andfat armature41 and its Workingcontactprepares a ,bridge across the' outgoingy trunk which :bridgeincludes the retardation coil 24 and the upper Winding of theelectropolarized relay 28. Relay 22, at armatures 39 vand 42 and theirresting contacts disconnects the battery-'feed relay 25 and at itsWorking ycontacts connects the calling device directly across the :trunkconcluetors and 46. Arcircuit may now be ytraced for operating relay 27of the lineswitch LS as follows: from ground, resting contact ofarmat-ure 49 and said armature, conductor 46, Working Contact ofarmature 42 and said armature, Working cont-act of the dial key DKcontrolled by springs 34 and said spring, the impulse springs of thecallingv device CD, spring 32 of .the.calling device key, DK and itsWorking contact, armature .89 and its Working' contact, conductor 45,armature 47 and its resting contact, and Winding of re` lay 27 tobattery. Relay'27 energizes and closes a circuit for t-he switchingrelay 26 and the stepping magnet 28 in series at armav ture 51, andconnects the Wiper 54 to the junctions of the switching relay 26 andstepping magnet 28 at-armature 50.

The operation of the linestvitclrV LS depends upon the busy or idlecondition-of the trunk upon which the lineswitch Wipers are resting. Incase the trunk upon Which the Wipers of the linesWitch are resting isidle, switching relay 26 energizes immediately. Assuming the relay 26 isshort circuited from ground at the test Wiper 54 and does not energize.The Wipers 53, 54, and 55, are rotated step-bystep in a buzzer likemanner by the action of the stepping magnet 28, Which operates fromground on the busy test contacts encountered by the testvviper-54.yl/VhenA an idle trunk is reached,-Which will be assumed torbev thetrunk.comprising-conductors 56, 57, and 58, thestepping magnet 428 Willstop its stepping operation, and relayv26j, being no longer shortcircuited,-energizes in series With stepping magnet 28.A Stepping magnet28 -does not operate at this time on account of tie high resistance ofthesvvitching relay 26. Relay 2 6, upon energizing, opens the trunk tobe busy, switching' iis 49 'and at armature 48 prepares a holdingcircuit for itself. At armatures 47 and 49, relay 26 disconnects theline conductors 45 and 46 from the winding of the line relay 27 andground, and extends them by way of wipers 53 and 55, conductors 56 and58 to the line relay of the selector in which the selected trunkterminates. The line and release relays of the selector energize inknown manner and the release relay connects ground to conductor 57,thereby completing the holding circuit for relay 26 before relay 27falls back.

The operator may now dial the digits oi the desired number. Responsiveto dialing, the selector and other automatic switches necessary toextend the connection to the desired line are operated in the well knownmanner. During the operation of the calling device CD the shunt springG2 engages its working contact thereby causing the operation ot relay inthe operators circuit. The operation oit relay 60 causes the circuit tothe operators headset to be opened at armature 61 and its restingcontact. Although this operation is of no utility at this time, it isessential when the operator dials on other trunk circuits (not shown)with which the headset is intended to be used.

llVhen the operator has finished dialling, she restores the dialling keyDK.V Since relay 22 is now energized, the normal short circuit aroundthis relay is not again closed, due to the open Contact at armature 40.

`When the dial key is restored the calling device bridge is replaced bythe bridge previously mentioned, including relays 23 and 24. Theelectropolarized relay 23 is not en ergized because the flow of currentthrough said relay is in the wrong direction.

Then the called party answers, respon-A sive to ringing current appliedby the connector switch7 which is the last switch in the train operatedby the operator, the back bridge relay in the connector switch energizesand reverses the direction ofcurrent flow in conduct-ors 45 and 46 inthe regular way. The iiow of current is now in the proper direction toenergize relay 23. i

At armature 43, relay 23 opens the circuit of the supervisory lamp L2,thereby notify ing the operator that the called party has ans 'ered. Thecalling and called parties may now converse with each other desired.

Upon the termination of conversation and responsive to the hanging up ofthe receiver by the called party the back bridge relay of the connectorreleases and reverses the current Vflow over conductors 56 and 58 sothat the yelectropolarized relay 23 deenergizes. Relay 23, upondeenerg'izing, again closes the circuit forY supervisory'lamp L2 atarmature 43 and its resting contact. The operator, upon observing thelighted condition of lamp L2, removes the plug P from the jack J therebyopening the circuit of relays 20 and 22. Relay 22, upon deenergizing,opens the circuit of the supervisory lamp L2, and at its other armatures39, 41, and 42 opens the bridge from across the trunk conductors 45 and4G. The removal of the bridge across the trunk conductors 45 and 4Gresults in the release of the line switch LS and the automatic switchesused in extending the call. 1When relay 2O deenergizes, the cord circuitCC is available `for extending other calls.

Responsive to the removal oi' the plug l? from the `iack J, the circuitof relays 6 and 7 opened. Relay 6 deenergizes but relay 7- is maintainedenergized over armature 17 and its working contact. Assuming that thecalling party has hung up his receiver, relay 4 deenergizes after aninterval responsive to the opening of its circuit at armature 15. TWhenrelay 4 deenergizes, said relay opens at armature 9 and its workingcontact the locking` circuit ot' relay 7 whereupon relay 7 deenergizes.

ssuming, however, that the calling party for somereason does not replacehis receiver and wishes to again talk with the operator, under suchconditions relay 5 energizes over the calling partys loop as soon asrelay 6 deenergizes. Relay 5, upon reenergizing, closes at armature 12and its working contact the circuit for maintaining slow acting relay 4energized; and at armature 10 and its working contactcloses a circuitfor lighting the hold lamp L as follows: from ground working contact ofarmature 10 and said armature, armature 16 and its working contact tolamp L and battery. At armature 8 and its workinS1 contact relay 4maintains ground on release conductor 2 thereby holding the switchesoperated by the calling party. rllhe operator again inserts the plug Pinto the jack J and converses with the calling party and extends thecall in the same manner as previously described if the same is desired.

When the calling party hangs up after the removal orn the plug P slowacting relay 4 -deenergizes after an interval and removes ground fromthe release trunk conductors 2 thereby allowing the switches operated bythe calling party to release in the well known manner.

In small telephone systems, as suggested in the lirst paragraphs of thisspecification, the operator may be required to perform special dutiesand accordingly it may so happen that the operator desires to beconnected with a subscriber in the automatic exchange. The cord circuitCC is arranged so that it is unnecessary or the operator to plug in onan idle ack in order to complete a connection to a called subscriber.Assuming that the operator at the switchboard wishes to converse withsome subscriber in the exchange, the operator will operate her dial keyDK and dial the digits necessary to complete the con nection to thecalled subscriber. 1iiiesponsive to the operation of the dial key DK acircuit is closed for relays 21 and 22 as follows: from ground throughwinding of relay 22, spring 33 of the dial key DK and its workingcontact, working contact of armature 37 and said armature, and windingof relay 21 to battery. Relay 21, upon energizing, closes a lockingcircuit for itself and relay 22 at armature 38 and its working contactthrough the spring 30 and its resting Contact of the talking key TK.Relay 22, upon energizing, at armature 40and its working contact, closesa circuit for the lower winding of polarized relay 23. Relay 23 will notenergize over this circuit on account of it being an electropolarizedrelay. Relay 22, at armature 40 and its resting contact, opens a pointin the shortcircuit around itself so that it will be maintainedenergized when the dial key DK is restored to normal position. Atarmature 41 and its working Contact, relay 22 prepares a bridge acrossthe trunk conductors 45 and 46 for holding the automatic switches. Atarmatures 39 and 42, relay 22 bridges the calling device CD across thetrunk conductors 45 and 46 thereby causing the operation of thelineswitch as has been previously eX- plained.

The operator now dials the digits required to extend the call to thedesired subscriber. In response to the digits dialled by the operator,the selector s vitch seized by the lineswitch LS and other switchesrespond to extend the talking connection. The last switch, being aconnector switch, operates to complete the connection to the calledsubscribers ine; signals the called subscribers line; and finallycompletes the talking connection when lthe called subscriber removes hisreceiver, as

is well known in the art.

When the operator has completed dialling the desired subscribers number,she restores the dial key DK to normal. In so doing, electro-polarizedrelay 23 is bridged across the conductors 45 and 46 inseries with theretardation coil24, relay 22 being in operated position. rlhis bridgeserves to hold the auton'i'atic switches in the established connection.between the operator and the called subscriber direction of thiscurrent flow however is o .i-

posite to that necessary to canse the operation of relay 23; relay 23,therefore, remains inoperative at present. `In response to the removalof the receiver of the called substation, a relayY operation in theconnector switch takes place, which reverses the current flow over thetrunk conductor 45 and 46 and through the winding of relay 23. Thisresults in the operation of relay 23 which opens the circuit of the lampL2 at armature 43` The extinguishing of the lamp L2 indicates to theoperator that the called subscriber has answered. The operator, uponobserving the extinguishing of the lamp L2, throws the talk key TK totall-:ing position thereby connecting her headsetdirectly across thetrunk conductors 45 and 46.

Responsive to the operation of talk key TK the locking circuit of relays21 and 22 is opened at spring 30 and its resting contact. Relay 21deenergizes but relay 22, however, is maintained energized over thefollowing circuit: from ground through winding of relay i 227 spring 30of talk key TK and its working Contact, armature 36 and its restingcontact, resistance 35 to battery.

The operator and the called subscriber may now converse. l/V henconversation is nished the operator restores the talk' key TK to itsnormal position, whereby' the circuit for relay 22 is opened at springs30 ofthe talk kej,1 TK. When relay 22 deenergizes, said relay removesthe bridge from across the conductors 45 and 46 thereby allowing theswitches to release in the manner as previously explained.

Having described the invention, its utility and operation, what isconsidered new and is desired to have protected by Letters Patent willbe set forth in the appended claims.

What is claimed is:

1. ln a telephone system, a cord circuit eX- tending to an automaticswitch, a dialling key and a talking key in said 'cord circuit, meansresponsive to the operation of said dialling key for initiatingtheoperation of said switch, means for holding the switch after thedialling key is restored, and means whereby the release of said switchis controlled by the subsequent operation of said talking key to itstalking position and then to its normal posit-ion.

2. In a telephone system, a cord circuit terminating at one end in alineswitch` a dialling key and a talking key in said cord circuit, arelay in said cord circuit having contacts for connectino` saidlineswitch to the talking conductors or said cord circuit, means responsiveto the operation of said dial key for energizing said relay to closesaid contacts to initiate the operation of said lineswitch, means formaintaining said relay energized after said dial key is restored tonormal, means for maintaining said relay energized after the talkinglkey has been operated to talking position; and means responsive to therestoration of the talking key to normal position for deenergizing saidrelay whereby said line switch is restored to normal position.

3.` In a telephone system, a cord circuit for use in connecting acalling party and a called party, a relay and a key individual to saidcord circuit, a shunt circuit around said relay, contacts controlled bysaid key when actuated for opening said shunt circuit, a circuit forenergizingv said relay when the shunt circuit is opened, and means formaintaining said relay energized during conversation between the callingand called parties.

l. In a telephone system, a single plug ended cord circuit terminatingin one end in a plug and in the other end in outgoing trunk conductors,said conductors normally disconnected from the talking conductors ofsaid cord circuit, a relay and a key individual to said cord circuit, ashunt circuit around said relai, contacts controlled by said key whenactuated for opening said. shunt Icircuit, circuit for energizing saidrelay when the shunt circuit is opened, a calling device bridged acrosssaid trunk conductors responsive to the actuation of said key and relay,contacts in said shunt circuit opened by said relay whereby said relayis maintained energizedafter the key is restored, and a second bridgeclosed across said'trunk conductors'through contacts of said relay whenthe key is restored.

. 5. In a telephone system, a cord circuit at an operators position, adialling key, a talking key, a first relay, and a second relay in saidcord circuit, means for energizing said relays responsive to theoperation of said dialling key, means for maintaining said relaysenergized after the restoration of said dialling key, means fordeenergizing said second relay and for maintaining said first relayenergized responsive to the operation of said talking key, and means fordeenergizing said first relay responsive to the restoration of saidtalking key.

6. In a telephone system, a cord circuit at an operators position, adialling key, a talking key, a first relay, and a second relay in saidcord circuit, means for energizing said relays responsive to theoperation of said dialling key, means for maintaining said relaysenergized afterV the restoration of said dialling key, means fordeenergizing said second relay and for maintaining said first relayenergized responsive to the operation of said talking key, means fordeenergizing said first relay responsive to the restoration of saidtalking key, trunk circuits terminating at said operators position, andmeans for rendering only said first relay responsive to the operation ofsaid dialling key and for rendering the control of said first relay bysaid talking key ineffective whenever said cord circuit is connectedwith any one of said trunk circuits.

7. In a telephone system, a cord circuit at an operators position, adialling key, a talking key, a first relay, and a second relay in saidcord circuit, means including a local circuit in said cord circuit forenergizing said first and second relays in series responsive to theoperation of said dialling key, contacts on said second relay forclosing a second local circuit to maintain said relays energized afterthe restoration of said dialling key, means for opening said secondlocal circuit to deenergize said second relay and for maintaining saidfirst relay energized over a third local circuit responsive to theoperation of said talking key, and means for opening said third localcircuit to deenergize said first relay responsii'etothe restoration ofsaid talking key.

8. Ina telephone system, a cord circuit at an operators position, adialling key, a talking key, a first relay, and a second relay in saidcord circuit, means including a local circuit in ksaid cord circuit forenergizing said first and second relays in series responsive to theoperation of said dialling key, contacts on said second relay forclosing a second local circuit to maintain said relays energized afterthe restoration of said dialling key, means for opening said secondlocal circuit to deenergize said second relay and for maintaining saidfirst relay energized over a third local circuit responsive to theoperation of said talking key, means for opening said third localcircuit to deenergize said first relay responsive to the restoration ofsaid talking key, trunk circuits terminating at said operators position,and means for opening said local circuits Vto render the sameineffective whenever said cord circuit is connected with any one Vofsaid trunk circuits.

9. In a telephone system, a trunk line terminating at one end in a plugending cord circuit at an operator-s position and terminating at theother endin an automaticswitch, relay in said trunk line, means foroperating said relay only in case the operator initiates a call withoutinserting said plug in any ack at said position, and means forthereafter automatically operating said switch to use said trunk line asan outgoing trunk line.

l0. In a telephone system, a trunk line terminating at one end in a plugending cord circuit at an operators position and terminating at theother end in an automatic switch, other trunk lines terminating at saidposition in jacks, said cord circuit used for answering calls extendedover said other trunk lines and for extending such calls by way of saidswitch, a relay in said cord circuit, means for operating said relayonly in case the operator at said position initiates a call herselfwithout inserting said plug in any jack at said position, and means forthereafter automaticallyoperating said switch to extend the connectionresponsive to the initiation of the operators call.

1l. In a telephone system, a trunk line terminating at one end in a plugending cord circuit at an operators position and terminating at theother end in an automatic switch, an operators impulse sender at saidposition, a dial key in said cord circuit, a circuit controlled by saidkey for connecting said sender to said cord circuit while the senderremains in normalposit-ion, and means for operating said switch toextend a connection responsive to the operation of said dial key mamWhenever the operator, initiates av call herself Without inserting saidplug of the cord'circuit in 'any jack at said position and Withoutoperatingsaid sender.

5 l2.- In a telephone system, a cord circuit terminating at one end in aplug and terminatingat the other end in an automatic switch, meansincluding the plug of said cord Circuit for answering calls, meansincluding an vop- 10 erators impulse sender and said switch forextending such calls, and means including said sender for operating saidswitch to eX'- tend ya connection Without completing any connection tothe plug of said oord circuit and .1 5 Without operating said sender.

13. Inv a telephone system, a cord circuit terminating in one end in anautomatic switch, altallring key in said oord circuit, means forinitiating the operation of said 2G switch, means for holding the switchin operated position, and means whereby the release of'said switch iscontrolled by the subsequent opera-tion Vof said talking key to itstalking position and then to its' normal posit-ion.

' lIn Witness whereof! I hereunto subscribe my naine this 21st day ofOctober, A. D.,

HARRY R.. PARSHALL.

